Portable personal computers (PCs) were first introduced in the early 1980s and have since enjoyed great commercial success and consumer acceptance. As the portable PC market has grown, users have begun to demand lighter weight, lower volume PCs which can be used for longer periods of time between battery charges. Meeting these demands has proved challenging in view of the fact that most portable PCs now support peripheral devices previously available only on desktop PCs. The additional peripherals greatly increase overall power consumption, making it difficult to achieve an optimal level of functionality while maintaining an acceptable battery life. Furthermore, although for reasons other than maximizing battery life, it has become desirable to more efficiently manage power consumption of desktop PCs in order to minimize overall operating costs.
Because many of the components and peripheral devices of both desktop and portable PCs consume a great deal of power even when they are not active, power management systems have been developed which cause each component or peripheral device to operate in the lowest power consumption mode with respect to present demands on the system. For example, U.S. Pat. No. 4,980,836 to Carter et al. discloses a power management system for a portable PC system in which the hard disk unit, the floppy disk unit, the keyboard, the serial ports and the printer are monitored for I/O activity to determine whether the system is active and a timer is reset upon each access to any of the monitored devices. If the timer counts down to zero, the system is deemed inactive and is placed in a reduced power consumption mode, in which power is removed from the hard disk unit, the floppy disk unit, the LCD and miscellaneous circuitry and clocks. To bring the system out of the reduced power consumption mode, a user depresses a switch to initiate a wakeup operation.
Since Carter, improvements in the basic power management system have been introduced which include options such as blanking the liquid crystal display (LCD) or monitor screen after a preselected period of I/O inactivity or turning off the hard disk drive motor alter the hard disk drive has not been accessed for a preselected period of time. Furthermore, there may be provided more than one reduced power consumption mode. For example, there may be a "STANDBY" mode, in which certain components, such as the LCD and the hard disk drive motor, are caused to enter a reduced power consumption mode but the processing speed of the central processing unit (CPU) is not affected, and a "SLEEP" mode, in which nearly all of the functions of the PC are slowed or halted, including the CPU. From the standpoint of power consumption, the SLEEP mode is substantially equivalent to turning the PC off, except that no data is lost.
It may be desirable in many cases to monitor each of a selected group of PC components and cause that component to operate in a reduced power consumption mode if it has not been accessed during a preselected time period. Therefore, what is needed is a system for efficiently monitoring each of a plurality of PC I/O and peripheral devices individually and causing the device to operate in one or more reduced power consumption modes, depending on the type of device, if it is determined that the device has not been accessed during a preselected time period.